Electromagnetic induction apparatus



May 18, 1943. A. F. MITTERMAIER ELECTROMAGNETIC INDUCTION APPARATUS Original Filed March 9, 1940 Invemtor: Armin F. Mittermaier,

n by I His Attorneg.

Patented May 18, 1943,

ELECTROMAGNETIC INDUCTION APPARATUS Armin F. Mittcrmaier, Fort Wayne, Ind., assignor to General Electric Company, a corporation of New York Original application March 9, 1940, Serial No.

323,235. Divided and this application Septemher 5, 1940, Serial No. 355,525

6 Claims. (Cl. 175356) I v This application is a division of my copending gpplication, Serial Number 323,235, filed March My invention relates to electromagnetic induction apparatus.

It is an object of my invention to provide improved, butuless expensive electromagnetic induction apparatus, such as reactors and transformers in smaller size particularly. Another object of my invention is to provide such apparatus which shall be quiet, have its laminations of magnetic sheet material tightly locked without the use of clamps or wedges and shall have improved insulation characteristics and definitely fixed air gaps. Other and further objects and advantages will become apparent as the description proceeds.

In carrying out my invention in its preferred form I assemble stacked laminations with a preformed form-wound electrical coil. Two stacks of laminations are utilized which have legs projecting into the coil from opposite ends of the coil window and have a fixed air gap between the tip ends of the laminations. The laminations are E-shaped with the center legs of the E occupying the coil window, the yokes and outer legs of the E forming a shell surrounding the coil in a plane parallel to the electrical axis oi the coil. For making a tight fit of the laminations in the coil window, the top and bottom pairs of lamlnations have their legs crimped or bent so that the springiness of the top and bottom laminations serves to clamp the laminations forming the core tightly together within the coil window as well as outside the coil window. The outside legs may be crimped slightly more than the inside legs in order to assure rigidity of the outside legs and and the magnetic laminatlons in successive stages of the assembling process.

In the drawing, Figure 1 illustrates a completed device which may be either-a reactor for use in apparatus such as fluorescent lamps or a transformer such as an audio transformer for radio purposes. In such types of apparatus it is desirable to maintain a certain predetermined air gap. For convenience the device will hereinafter he referred to as a reactor although my invention is not limited thereto. It comprises a com ductive-wlnding structure or electrical coil ll which is a preformed form-wound coil and may, therefore, be produced in a rapid, economical manner well known to the art with the requisite amount of insulation included therein. The coil ll has a window for receiving a magnetic core. The complete magnetic circuit of the device illustrated in Figure 1 consists of magnetic core material substantially filling the coil window l2 and core material providing a magnetic return path around the outside of the coil ll. circuit consists of a pair of E-shaped stacks of laminations l3 and it. Each lamination of the stack is shown more in detail in Figure 2, having a middle leg or arm it which lies within the coil window, an outer leg or arm it and a yoke porfreedom from vibration or noise in alternating current circuits.

The invention will be understood more readily from the following detailed description when considered in connection with the accompanying v drawing and those features of the invention which are believed to be novel and patentable will be pointed out in the claims appended thereto.

In the drawin Figure 1 is a perspective view of a reactor constructed in accordance with one embodiment of my invention.

Figure 2 is a plan view of one of the E-shaped laminations employed in the apparatus of Figure 1. 1

Figures 3 and 4 are perspective views and 5-7, inclusive, are longitudinal sectional views partinlly schematic illustrating the electrical coll tion it joining the middle and out 1' legs. The end of the middle leg 05 of each amination is preferably tapered as shown at it in order that the middle leg may be guided into the coil window l2 more easily. In the manner which will be explained more in detail hereinafter laminations at the top and at the bottom, e. g'., the

top and bottom pal-rs of laminations i8 and i9 have the middle legs crlmped toward each other to facilitate further guiding the middle leg of the group of lam-inations into the coil window. Although I have found it satisfactory to crimp two laminations at the top and two at the bottom of the group, my invention is not limited to this exact number. the E-shaped lamlnations l8 and I9 but also the outer legs; as shown in Figure, 1, may, if desired, be crimped for the purpose of causing the laminations to fit snugly into the coil window l2 and causing the outer legs Hi to be held tightly to prevent vibration and noise when an alternating current is applied to the electrical coil H. The

crlmps in'the outer legs somewhat sharper than the crimps in the middle arms.

.One of the first steps in the method of assem- Y The magnetic Not only themiddle legs of bling the laminations with the electrical coil consists briefly of gauging the requisite height of laminations to form half the core and to fill the coil window l2 substantially, thus forming a group of laminations 2i as illustrated in Figure 3..

The top and bottom pairs of laminations i8 and I 9 are placed against the other laminations in the group in such a manner that the ends of the legs of the E project beyond the remainder of the laminations 22 in the group. This stage is illustrated in Figure 4. The ends of the legs of the laminations ar bent over to form the crimps 20, which-is the stage illustrated in Figure 5. Then the laminations in the groups of laminations 2| as units have the middle legs netic gap spacer may be inserted in the coil to fill the air gap. The gap spacer may be inserted either in solid or plastic form. Preferably before the laminations are inserted into an electrical coil a quantity of suitable cement 23 is placed opposite the coil window, as illustrated in Figure 5, or within the coil window so that the cement 23 will fill the space within the coil window not occupied by the magnetic material, thus making certain that the laminations are very tightly held and cannot vibrate within the coil window and that. there are no air pockets to retain 'or collect air, moisture or substances which may interfere with the insulation or cause corrosion. My in- 'vention' is not, however, limited to utilizing both the features of crimped lamination legs and cement filling, as a tight rigid construction may be made by the use of one of these features alone.

A more complete description of this method of forming the reactor together with a description of the apparatus employed in forming the reactor, portions of the apparatus being shown in Figures 3 to 7 inclusive, will be found in my above mentioned copending application which also contains claims directed to the method and apparatus If it is desired to fix the reactance of the reactor withla high degree of accuracy; the air gap 245 may be left slightly higher than the anticipated value by using a slightly thicker gap spacer 25, and the laminations may then be moved closer by means of adevice o. able fixture having a fine screw to permit gradual shortening of the air gap until the propervalue ther suitr.

of reactance is obtained. If this procedure is carried out it must be done sufliciently soon after the reactor is removed from the assembling machine before the cement-fllling the window in the space between the laminations in the coil window has had an opportunity to harden. If the reactance is to be precisely adjusted in the manner just suggested, the coil may be connected in an electrical circuit for measuring reactance while the air gap is being given its final adjustment. In order to set the cement the reactor may be given a heat treatment, and to improve the insulating properties of the coil the reactors may thereafter be treated with rosin and finally impregnated with a suitable insulating compound, or the cement may be allowed to set while the coil is being treated.

My invention is not limited to any particular size of stationary induction apparatus. However, I have obtained satisfactory results pertaining to reactors for use with fluorescent lamps. In this case the core consists of about'20 laminations 1" x 1%", forming a /2" stack, with the center laminations about wide and with the outer laminationsiabout A" wide. The gap is made about .012 of an inch to produce a reactor of .71 henry for 15 watt 110 volt lamps and about .015 of an inch to produce a reactor of about .61 henry for 20 watt 110 volt lamps. A satisfactory composition of cement was found to be a mixture of 2 parts Portland cement by weight and 1 part of Bakelite varnish, designated by the Bakelite Company as BV-6509. The cement was found to penetrate well, strongly adhering to the lamination tips, which make a butt joint with the magnetic-gap-fixing cement between the lamination tips, and there was found to be no need for wedging or clamping of the laminations to obtain freedom from noise or vibration;

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. Electromagnetic induction apparatus comprising a form-wound conductive-winding structure or coil having a, substantially rectangular window therein, a pair of groups of core laminations of E shape, and-impregnating cement,'the

groups of laminations each having the middle legs of the E inserted in the coil window and extending toward the corresponding legs of the other group with a fixed gap between opposite leg tips, the middle leg substantially filling the coil window, the top and bottom laminations of the groups having their legs bent toward each other with the outer legs bent more than the inner legs, whereby .the laminations are securely wedged in the coil window and the portions of the laminations both within and surrounding the coil are securely held together, whereby the laminations are locked and noise is prevented, the said cement impregnating the space within the coil winbetween the tips of the opposite legs, the middle leg substantially filling the coil window, the top and bottom laminations of the groups having 3. Electromagnetic induction apparatus i Come prising a form-wound conductive winding strut-j ture or coil having a window therein to-receive} a magnetic core, a pair of groups of core lamina tions having leg portions adapted to fit in the conductive winding structure and gap spacing means, the groups of iaminations each having the said legs inserted in the coil window and extending toward the corresponding legs of the other group with the tips of the opposite legs in tight contact with opposite sides or the gap spacing means, said legs substantially filling the coil window, the top and bottom laminations of the groups having their legs bent toward each other, whereby the laminations are securely wedged in the coil window, the groups of laminations are joined by the winding structure, and the portions of the laminations within the winding structure are securely held together preventing transverse or longitudinal vibration and attendant noise.

4. Electromagnetic induction apparatus comprising a formwound conductive winding structure or coil having a window therein to receive a magnetic core, a pair of groups of core laminations having leg portions adapted to fit in the conductive winding s ncture, the groups of laminations each having the said legs inserted in the coil window and extending toward the corresponding legs of the other group with a fixed a gap between the tips oi the opposite legs, said legs substantially filling the coil window, the top and bottom laminations o! the groups having their legs bent toward each other, whereby the laminations are securely wedged in the coil window, the groups of laminations are joined by the winding structure and the portions of the laminations within the winding structure are securely held together preventing noise and vibration.

5. Electromagnetic induction apparatus comprising a form-wound conductive winding structure, a coil having a substantially rectangular window therein, a group of core laminations of E shape having the middle legs of the E inserted in the coil window and substantially filling the A coil window, the top and bottom laminations of the group having their legs bent toward each other with the outer arms bent more than the inner'legs, whereby the inner legs are wedged in the coil window and the laminations both within and surrounding the coil are securely held together, whereby the laminations are locked and noise is prevented.

6. Electromagnetic induction apparatus comprising a conductive winding structure or coil having a substantially rectangular window therein, a group of core laminations of 'E shape having the middlelegs of the E inserted in the coil window and substantially filling it, the laminations at the top and bottom or the group having legs which are bent. toward each other to form crimps whereby the laminations are securely wedged in the coil window and are held together.

J ARMIN'F. -l 

